[petsc-users] KSP diverging

[Matthew Knepley]

On Thu, Dec 22, 2011 at 7:51 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Thu, Dec 22, 2011 at 19:46, Matthew Knepley <knepley at gmail.com> wrote:
>
>> dtol failure is impossible for GMRES (and CG). Consider checking with
>> that.
>
>
> Well, if you turn of restarts in GMRES and if orthogonalization is working
> correctly.
>

Even if you lose orthogonality, it will just stagnate since you always have
the solution
from the first few vectors. Likewise, I do not see how you can get an
diverging sequence
from restarting since you always have the last residual, you just stagnate.

   Matt

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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